Implementation and QA of the XKnife system for stereotactic irradiation

Practices were described concerning the treatment until July, 1998, of 33 lesions of 27 patients with stereotactic irradiation with XKnife system version 3 (Radionics) which had been introduced into authors' facility in April, 1997, together with its quality assurance (QA) before operation, choice of stereotactic radiosurgery (SRS)/ stereotactic radiotherapy (SRT), dose selection and experience and/or problems. Before actual operation, training abroad, in-house conferences, collection of fundamental data for Radionics and so on were performed. The XKnife system was equipped on the Varian Clinac 2100C and was of BRW head ring assembly, GTC relocatable head frame, depth helmet and the computer HP 9000C110. QA required for every operation was followed by 12 check-lists involving confirmation of stability and target accuracy of laser, of accuracy of gantry and rotating speed of bed and of reproducibility of head localizaion. XKnife treatment was carried out according to the scheme computed by previous CT, MRI and angiographic images. Case-by-case consideration was necessary for choice of SRS and SRT. The marginal dose was principally 80% isodose and linear quadratic model was used for determination of the dose and fractionation. Establishment of a team for the system was pointed out to be necessary. (K.H.)